Hall measurement is one of the most essential characterization techniques in electronics material device research and industry especially for semiconductor and solid state device research. A rotating parallel dipole line (PDL) high sensitivity Hall system has been developed for the characterization of very low mobility and insulating films which works based on the generation of an oscillating magnetic field and lock-in detection of the tiny Hall signal oscillation in the presence of large background noise. See, for example, U.S. Pat. No. 9,041,389 issued to Gokmen et al., entitled “Hall Measurement System with Rotary Magnet” (hereinafter “U.S. Pat. No. 9,041,389”), the contents of which are incorporated by reference as if fully set forth herein. The PDL-based system described in U.S. Pat. No. 9,041,389 is implemented using a pair of transversely magnetized magnets where each magnet produces a “dipole line” magnetic field. One of the magnets is connected to a motor and gearbox, and the other rotates freely following the motor-driven magnet through ferromagnetic coupling.
This system only yields a standard set of results in a Hall measurement, i.e., majority carrier type, density, and mobility. However, for some applications such as the development of solar cell devices, minority carrier information (e.g., mobility, density and recombination lifetime) are also important as they determine the quality of the solar cell. Thus extraction of the minority carrier information is also desired.
Furthermore, this motor and gearbox set-up limits application of the system in cases where the experimental space is confined and/or temperature-controlled. For instance, it is desirable to be able to perform similar AC field/PDL Hall measurements with a measurement or cryostat chamber for temperature-dependent studies. However, these studies would involve small sample spaces at low temperatures, also normally in a vacuum. The small sample space limits the mechanics that can be included with the system, and the low-temperature conditions affect the operation of components such as an electric motor.
Therefore, an improved alternating current (AC) field/PDL Hall system would be desirable.